diff --git a/spring-boot-actuator/src/main/java/org/springframework/boot/actuate/audit/InMemoryAuditEventRepository.java b/spring-boot-actuator/src/main/java/org/springframework/boot/actuate/audit/InMemoryAuditEventRepository.java
index a7dc37b5ab7..b17c76aa742 100644
--- a/spring-boot-actuator/src/main/java/org/springframework/boot/actuate/audit/InMemoryAuditEventRepository.java
+++ b/spring-boot-actuator/src/main/java/org/springframework/boot/actuate/audit/InMemoryAuditEventRepository.java
@@ -16,54 +16,67 @@
 
 package org.springframework.boot.actuate.audit;
 
-import java.util.ArrayList;
-import java.util.Collections;
 import java.util.Date;
-import java.util.HashMap;
+import java.util.LinkedList;
 import java.util.List;
-import java.util.Map;
 
 /**
  * In-memory {@link AuditEventRepository} implementation.
  *
  * @author Dave Syer
+ * @author Phillip Webb
  */
 public class InMemoryAuditEventRepository implements AuditEventRepository {
 
-	private int capacity = 100;
+	private static final int DEFAULT_CAPACITY = 4000;
 
-	private final Map<String, List<AuditEvent>> events = new HashMap<String, List<AuditEvent>>();
+	/**
+	 * Circular buffer of the event with tail pointing to the last element.
+	 */
+	private AuditEvent[] events;
+
+	private volatile int tail = -1;
+
+	public InMemoryAuditEventRepository() {
+		this(DEFAULT_CAPACITY);
+	}
+
+	public InMemoryAuditEventRepository(int capacity) {
+		this.events = new AuditEvent[capacity];
+	}
 
 	/**
 	 * @param capacity the capacity to set
 	 */
-	public void setCapacity(int capacity) {
-		this.capacity = capacity;
+	public synchronized void setCapacity(int capacity) {
+		this.events = new AuditEvent[capacity];
 	}
 
 	@Override
-	public List<AuditEvent> find(String principal, Date after) {
-		synchronized (this.events) {
-			return Collections.unmodifiableList(getEvents(principal));
-		}
-	}
-
-	private List<AuditEvent> getEvents(String principal) {
-		if (!this.events.containsKey(principal)) {
-			this.events.put(principal, new ArrayList<AuditEvent>());
-		}
-		return this.events.get(principal);
-	}
-
-	@Override
-	public void add(AuditEvent event) {
-		synchronized (this.events) {
-			List<AuditEvent> list = getEvents(event.getPrincipal());
-			while (list.size() >= this.capacity) {
-				list.remove(0);
+	public synchronized List<AuditEvent> find(String principal, Date after) {
+		LinkedList<AuditEvent> events = new LinkedList<AuditEvent>();
+		for (int i = 0; i < this.events.length; i++) {
+			int index = ((this.tail + this.events.length - i) % this.events.length);
+			AuditEvent event = this.events[index];
+			if (event == null) {
+				break;
+			}
+			if (isMatch(event, principal, after)) {
+				events.addFirst(event);
 			}
-			list.add(event);
 		}
+		return events;
+	}
+
+	private boolean isMatch(AuditEvent auditEvent, String principal, Date after) {
+		return (principal == null || auditEvent.getPrincipal().equals(principal))
+				&& (after == null || auditEvent.getTimestamp().compareTo(after) >= 0);
+	}
+
+	@Override
+	public synchronized void add(AuditEvent event) {
+		this.tail = (this.tail + 1) % this.events.length;
+		this.events[this.tail] = event;
 	}
 
 }
diff --git a/spring-boot-actuator/src/test/java/org/springframework/boot/actuate/audit/InMemoryAuditEventRepositoryTests.java b/spring-boot-actuator/src/test/java/org/springframework/boot/actuate/audit/InMemoryAuditEventRepositoryTests.java
index 6753edfdc47..74dba50c3f8 100644
--- a/spring-boot-actuator/src/test/java/org/springframework/boot/actuate/audit/InMemoryAuditEventRepositoryTests.java
+++ b/spring-boot-actuator/src/test/java/org/springframework/boot/actuate/audit/InMemoryAuditEventRepositoryTests.java
@@ -16,30 +16,85 @@
 
 package org.springframework.boot.actuate.audit;
 
+import java.util.Calendar;
 import java.util.Date;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
 
 import org.junit.Test;
 
-import static org.junit.Assert.assertEquals;
+import static org.hamcrest.Matchers.equalTo;
+import static org.junit.Assert.assertThat;
 
 /**
  * Tests for {@link InMemoryAuditEventRepository}.
  *
  * @author Dave Syer
+ * @author Phillip Webb
  */
 public class InMemoryAuditEventRepositoryTests {
 
-	private final InMemoryAuditEventRepository repository = new InMemoryAuditEventRepository();
+	@Test
+	public void lessThanCapacity() throws Exception {
+		InMemoryAuditEventRepository repository = new InMemoryAuditEventRepository();
+		repository.add(new AuditEvent("dave", "a"));
+		repository.add(new AuditEvent("dave", "b"));
+		List<AuditEvent> events = repository.find("dave", null);
+		assertThat(events.size(), equalTo(2));
+		assertThat(events.get(0).getType(), equalTo("a"));
+		assertThat(events.get(1).getType(), equalTo("b"));
+
+	}
 
 	@Test
-	public void testAddToCapacity() throws Exception {
-		this.repository.setCapacity(2);
-		this.repository.add(new AuditEvent("phil", "UNKNOWN"));
-		this.repository.add(new AuditEvent("phil", "UNKNOWN"));
-		this.repository.add(new AuditEvent("dave", "UNKNOWN"));
-		this.repository.add(new AuditEvent("dave", "UNKNOWN"));
-		this.repository.add(new AuditEvent("phil", "UNKNOWN"));
-		assertEquals(2, this.repository.find("phil", new Date(0L)).size());
+	public void capacity() throws Exception {
+		InMemoryAuditEventRepository repository = new InMemoryAuditEventRepository(2);
+		repository.add(new AuditEvent("dave", "a"));
+		repository.add(new AuditEvent("dave", "b"));
+		repository.add(new AuditEvent("dave", "c"));
+		List<AuditEvent> events = repository.find("dave", null);
+		assertThat(events.size(), equalTo(2));
+		assertThat(events.get(0).getType(), equalTo("b"));
+		assertThat(events.get(1).getType(), equalTo("c"));
+	}
+
+	@Test
+	public void findByPrincipal() throws Exception {
+		InMemoryAuditEventRepository repository = new InMemoryAuditEventRepository();
+		repository.add(new AuditEvent("dave", "a"));
+		repository.add(new AuditEvent("phil", "b"));
+		repository.add(new AuditEvent("dave", "c"));
+		repository.add(new AuditEvent("phil", "d"));
+		List<AuditEvent> events = repository.find("dave", null);
+		assertThat(events.size(), equalTo(2));
+		assertThat(events.get(0).getType(), equalTo("a"));
+		assertThat(events.get(1).getType(), equalTo("c"));
+	}
+
+	@Test
+	public void findByDate() throws Exception {
+		Calendar calendar = Calendar.getInstance();
+		calendar.set(2000, 1, 1, 0, 0, 0);
+		calendar.set(Calendar.MILLISECOND, 0);
+		Map<String, Object> data = new HashMap<String, Object>();
+		InMemoryAuditEventRepository repository = new InMemoryAuditEventRepository();
+		repository.add(new AuditEvent(calendar.getTime(), "dave", "a", data));
+		calendar.add(Calendar.DAY_OF_YEAR, 1);
+		repository.add(new AuditEvent(calendar.getTime(), "phil", "b", data));
+		calendar.add(Calendar.DAY_OF_YEAR, 1);
+		Date after = calendar.getTime();
+		repository.add(new AuditEvent(calendar.getTime(), "dave", "c", data));
+		calendar.add(Calendar.DAY_OF_YEAR, 1);
+		repository.add(new AuditEvent(calendar.getTime(), "phil", "d", data));
+		calendar.add(Calendar.DAY_OF_YEAR, 1);
+		List<AuditEvent> events = repository.find(null, after);
+		assertThat(events.size(), equalTo(2));
+		assertThat(events.get(0).getType(), equalTo("c"));
+		assertThat(events.get(1).getType(), equalTo("d"));
+		events = repository.find("dave", after);
+		assertThat(events.size(), equalTo(1));
+		assertThat(events.get(0).getType(), equalTo("c"));
 	}
 
 }